TW201944474A - Wafer processing method capable of appropriately dividing a wafer to form a plurality of flash memory chips - Google Patents

Abstract

[Problem] To provide a method for processing a wafer capable of appropriately dividing a wafer on which a plurality of flash memory wafers are formed.
[Solution] A method for processing a wafer is composed of at least the following process: a cutting groove forming process, which is performed by cutting a predetermined division line (14) with a cutter (28) and forming a cutting groove (2) in the second memory layer (10). 30); the reforming layer forming process is to position the light-condensing point of the laser light (LB) with a wavelength penetrating to the semiconductor substrate (4) on the semiconductor substrate corresponding to the planned division line (14) ( 4), the semiconductor substrate (4) is irradiated with laser light (LB) to form a modified layer (42); the division process is to grind the back surface of the semiconductor substrate (4) to make cracks (60) from the modified layer ( 42) Grow and divide the wafer (2) into individual flash memory chips (12); and DAF division process, which is on the back of the wafer (2) that is divided into individual flash memory chips (12) (2b) The DAF62 is provided and the support tape (66) supporting the DAF62 is expanded to divide the DAF62 into each flash memory chip (12).

Description

Processing method of wafer

The invention relates to a method for processing a wafer, which comprises alternately stacking a first memory layer on a surface of a semiconductor substrate with a plurality of metal films and insulating films, and alternately using the insulating layer as a bonding layer on the first memory layer. A plurality of flash memory wafers formed by stacking a plurality of metal films and a second memory layer of an insulating film are divided into individual flash memory wafers by dividing a wafer divided by a predetermined line.

Devices such as ICs, LSIs, and flash memories are laminated on the surface of a semiconductor substrate such as silicon, and are generated in the form of a wafer by dividing a predetermined line to be divided. The wafer is divided into various devices by processing devices such as a laser processing device and a dicing device, and the divided devices are used in appliances such as mobile phones and personal computers.

Furthermore, a proposal has been made to locate a light-condensing point of laser light having a wavelength penetrating to the semiconductor substrate inside the semiconductor substrate, and irradiate the semiconductor substrate with the laser light, along the predetermined division line, inside the semiconductor substrate. After the modified layer is formed, the back surface of the semiconductor substrate is ground to be thinned, and a crack is grown from the modified layer to divide the wafer into individual devices (see, for example, Patent Document 1).
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-7330

[Problems to be Solved by the Invention]

The above-mentioned technology has the advantage of expanding the DAF (Die Adhesive Sheet of Adhesive Film) on the backside of the wafer divided into various devices, and dividing the DAF into the size corresponding to the device.

However, a first memory layer in which a plurality of metal films and an insulating film are alternately laminated on a surface of a semiconductor substrate, and a plurality of metal films and insulating films are alternately laminated on the first memory layer with the insulating layer as a bonding layer. When a plurality of flash memory chips composed of a second memory layer are divided by dividing a predetermined line and divided into individual flash memory chips, when using the above technology, there are some The crack zigzags in the bonding layer to reach the second memory layer, damages the second memory layer, and fails to properly divide the wafer into individual flash memory wafers.

An object of the present invention, which was created in view of the above-mentioned facts, is to provide a wafer processing method that can appropriately divide a wafer formed with a plurality of flash memory wafers.

[Means to solve the problem]

In order to solve the above problems, the present invention provides the following wafer processing method. That is, a wafer processing method, in which a first memory layer connected to a surface of a semiconductor substrate and alternately laminated with a plurality of metal films and insulating films, and alternately using an insulating layer as a bonding layer on the first memory layer A plurality of flash memory wafers formed by stacking a plurality of metal films and a second memory layer of an insulating film are divided into predetermined flash memory wafers by dividing a predetermined line, and the wafer is processed by It is characterized in that it is composed of at least the following process: a cutting groove forming process that uses a cutter to cut a predetermined division line to form a cutting groove in the second memory layer;
The reforming layer forming process is to position the light-condensing point of laser light with a wavelength penetrating to the semiconductor substrate within the semiconductor substrate corresponding to the predetermined division line, and irradiate the semiconductor substrate with laser light to form a reforming layer. Mass layer; segmentation process, which involves grinding the back of a semiconductor substrate to grow cracks from the reformer layer, and divide the wafer into individual flash memory chips; and DAF segmentation process, which involves dividing the wafer into individual flash memory chips The back of the wafer is equipped with DAF and the DAF support tape is expanded to divide the DAF into each flash memory chip.

In the cutting groove forming process, it is preferable that the cutting groove reaches the bonding layer.

[Inventive effect]

The method for processing a wafer provided by the present invention is composed of at least the following processes: a cutting groove forming process that uses a cutter to cut a predetermined dividing line to form a cutting groove in the second memory layer; a reforming layer forming process that is The light-condensing point of the laser light having a wavelength penetrating to the semiconductor substrate is positioned inside the semiconductor substrate corresponding to the predetermined division line, and the semiconductor substrate is irradiated with the laser light to form a modified layer; and a division process, which It is to grind the back of the semiconductor substrate to grow cracks from the reforming layer to divide the wafer into individual flash memory wafers; and DAF division process, which is arranged on the back of the wafer that is divided into individual flash memory wafers DAF expands the DAF support tape and divides the DAF into each flash memory chip, so the cracks grown from the reformed layer are not tortuously guided to the cutting groove, and the wafer can be appropriately divided into individual flash memories. Memory chip.

Hereinafter, the implementation mode of the wafer processing method of the present invention will be described with reference to the drawings.

FIG. 1 shows a wafer 2 that can be processed by the wafer processing method of the present invention. The disc-shaped wafer 2 has a plurality of flash memory wafers 12, which are connected to the surface of the semiconductor substrate 4 by a first memory layer 6 in which a plurality of metal films and insulating films are alternately laminated, and the first memory layer 6 is insulated on the first memory layer 6. The second memory layer 10 is a layer in which a plurality of metal films and an insulating film are alternately laminated as a bonding layer 8. The plurality of flash memory chips 12 are partitioned by a grid-like dividing line 14.

As the semiconductor substrate 4 of the wafer 2, for example, a silicon substrate having a thickness of about 400 μm can be used. As the first memory layer 6 and the second memory layer 10, it is preferable to alternately stack a total of 48 layers of a metal film and an insulating film with a thickness of about 10 μm, or alternately stack a total of 32 layers of a metal film and an insulating film to have a thickness of about 8 μm. . As the bonding layer 8, a nitride film, a SiO ₂ film, or the like having a thickness of about 1 μm can be used.

In the embodiment shown in the figure, a cutting groove forming process is first performed by cutting a predetermined dividing line 14 with a cutter and forming a cutting groove in the second memory layer 10. The cutting groove formation process can be performed using, for example, a part of the cutting device 16 shown in FIGS. 1 and 2. The dicing apparatus 16 includes a reel mounting table 18 that sucks and holds the wafer 2, and a cutting means 20 (see FIG. 2) that cuts the wafer 2 that is sucked and held on the reel table 18.

As shown in FIG. 1, a porous circular suction pan 22 connected to a suction means (not shown) is arranged on the upper end portion of the pan mounting base 18, and the suction unit 18 is arranged on the pan mounting base 18. A suction force is generated on the suction pad 22, and the suction is performed to hold the wafer 2 placed thereon. In addition, the disk mounting table 18 is rotated around the axis extending in the vertical direction by a disk mounting table motor (not shown), and is rotated by an X-axis feed means (not shown). Advance and retreat in the X-axis direction indicated by the arrow X in FIG. 1.

As shown in FIG. 2, the cutting means 20 includes a rotating shaft sleeve 24 extending in a Y-axis direction (a direction indicated by an arrow Y in FIG. 2) orthogonal to the X-axis direction, and a rotation centered on the Y-axis direction. The shaft 26 is freely supported by a shaft 26 of the shaft sleeve 24, a shaft motor (not shown) for rotating the shaft 26, and a ring-shaped cutter 28 attached to the front end of the shaft 26. The rotating shaft sleeve 24 is moved forward and backward in the Y-axis direction by a Y-axis feeding means (not shown), and is moved up and down in a vertical direction by a lifting means (not shown). The planes defined by the X-axis direction and the Y-axis direction are substantially horizontal.

As shown in FIG. 1 (a), in the cutting groove forming process, first, the surface 2 a of the wafer 2 is directed upward, and the wafer 2 is attracted and held on the upper surface of the disk mounting table 18. Next, the imaging device (not shown) of the dicing device 16 is used to image the wafer 2 from above. Based on the image of the wafer 2 imaged by the imaging device, the planned division line 14 is aligned in the X-axis direction, and the cutting blade is aligned. 28 is positioned above a predetermined division line 14 aligned in the X-axis direction. Next, the cutter 28 is rotated in a direction indicated by an arrow A in FIG. 2. Next, the rotary shaft sleeve 24 is lowered, the tip of the cutter 28 is cut to a predetermined division line 14 aligned with the X-axis direction, and the disk mounting table 18 is relatively opposed to the cutting means 20 at a specific feed speed at X A machining feed is performed in the axial direction, and a cutting process for forming a cutting groove 30 in the second memory layer 10 along the predetermined division line 14 is performed accordingly. The width of the cutting groove 30 is, for example, about 20 μm. The depth of the cutting groove 30 is at least the same as the thickness of the second memory layer 10 (for example, about 8 μm or about 10 μm), and the depth to the bonding layer 8 (for example, about 9 μm or about 11 μm). Better. Alternatively, as shown in FIG. 3, the cutting groove 30 may reach the first memory layer 6 beyond the bonding layer 8.

Next, the rotary shaft sleeve 24 is relatively indexed in the Y-axis direction with respect to the disk mounting table 18 only at the portion in the Y-axis direction that divides the predetermined line 14. Further, the cutting groove 30 is formed by repeating the cutting process and the index feed alternately along all the planned division lines 14 after the alignment in the X-axis direction. In addition, after rotating the disk mounting table 18 by 90 degrees, it is formed by alternately repeating cutting processing and indexing feed along all planned division lines 14 orthogonal to the planned division line 14 where the cutting groove 30 was previously formed. Cutting groove 30. In this way, a cutting groove forming process is performed, and the cutting grooves 30 are formed in a grid pattern along the grid-like planned division lines 14.

After the cutting groove forming process is performed, a modified layer forming process is performed. The modified layer forming process locates the light-condensing point of the laser light having a wavelength penetrating to the semiconductor substrate 4 so as to correspond to the planned division line 14 The semiconductor substrate 4 is irradiated with laser light inside the semiconductor substrate 4 to form a modified layer. The modified layer forming process can be performed using, for example, a laser processing device 32 which is partially shown in FIGS. 4 and 5. The laser processing apparatus 32 includes a disk mounting table 34 that sucks and holds the wafer 2, and a condenser 36 (see FIG. 5) that irradiates the laser pulse light LB to the wafer 2 that is sucked and held on the disk table 34. As shown in FIG. 4, at the upper end portion of the disk mounting table 34, a porous circular suction disk 38 connected to a suction means (not shown) is arranged. In addition, the disk mounting table 34 is configured to be rotatable and configured to move forward and backward in the X-axis direction and the Y-axis direction.

When continuing the description with reference to FIG. 4, in the modified layer forming process, first, a surface 2 a of the wafer 2 in which the cutting grooves 30 are formed in a grid pattern is attached with a circular protective tape 40 for protecting the flash memory wafer 12. . Next, the back surface 2b of the wafer 2 is directed upward, and the wafer 2 is sucked and held on the upper surface of the disk mounting table 34. Next, the imaging device (not shown) of the laser processing device 32 is used to image the wafer 2 from above. Based on the image of the wafer 2 imaged by the imaging device, the planned division line 14 is aligned with the X-axis direction, and The condenser 36 is positioned above a predetermined division line 14 aligned in the X-axis direction. At this time, although the back surface 2b of the wafer 2 faces upward and the surface 2a on which the planned division line 14 is formed faces downward, the imaging means by the laser processing device 32 includes an infrared irradiation means for irradiating the wafer 2 with infrared rays, and capture The optical system of infrared rays irradiated by the infrared irradiation means, and an imaging element (infrared CCD) that outputs an electric signal corresponding to the infrared rays captured by the optical system can pass through the back surface 2b of the wafer 2 and the predetermined division line of the imaging surface 2a 14.

Next, the condenser 36 is raised and lowered by means of a focusing point position adjusting means (not shown) of the laser processing device 32 to position the focusing point of the pulsed laser beam LB on the semiconductor substrate 4 corresponding to the planned division line 14. internal. Next, as shown in FIG. 5, while the disk mounting table 34 relatively feeds the condenser 36 in the X-axis direction at a specific feed rate, the condenser 36 is irradiated with respect to the semiconductor substrate 4. A pulsed set light LB having a penetrating wavelength is subjected to a modified layer forming process for forming a modified layer 42 inside the semiconductor substrate 4 along a predetermined division line 14. In addition, although the modified layer 42 is formed inside the semiconductor substrate 4 and does not substantially appear on the back surface, the image is represented by a chain line. The modified layer 42 has a lower strength than the surroundings, and further extends in the thickness direction of the semiconductor substrate 4 as shown in FIG. 6. Next, only the part which divides the space | interval in the Y-axis direction of the predetermined line 14, the disk mounting table 34 relatively feeds the condenser 36 in the Y-axis direction relatively. Further, the modified layer 42 is formed inside the semiconductor substrate 4 by repeating the cutting process and the index feed alternately along all the planned division lines 14 aligned in the X-axis direction. In addition, after rotating the disk mounting table 34 by 90 degrees, by repeating the reforming layer forming process and indexing feed alternately, all division plans are orthogonal to the dividing plan line 14 on which the reforming layer 42 was previously formed. The wire 14 forms a modified layer 42 inside the semiconductor substrate 4. In this way, a modified layer forming process is performed, and the modified layer 42 is formed in a grid pattern inside the semiconductor substrate 4 along the grid-like planned division line 14. Such a modified layer forming process can be performed under the following processing conditions, for example.
Wavelength of pulsed laser light: 1064nm
Repeated frequency: 80kHz
Average output: 1.0W
Feed speed: 400mm / s

After the modification layer formation process is performed, a division process is performed. The division process is to grind the back surface of the semiconductor substrate 4 (the back surface 2b of the wafer 2) to grow cracks from the modification layer 42 to divide the wafer 2 into flash memories. Body wafer 12. The division process can be performed using, for example, a part of the grinding device 44 shown in FIG. 7. The grinding device 44 includes a reel mounting table 46 that sucks and holds the wafer 2, and a grinding means 48 that grinds the wafer 2 that is sucked and held on the reel mounting table 46.

The chuck mounting table 46 is configured to attract and hold the wafer 2 on the upper surface and rotate freely. The grinding means 48 includes a rotating shaft 50 connected to a rotating shaft motor (not shown) and extending in the up-down direction, and a disk-shaped roller bracket 52 fixed to the lower end of the rotating shaft 50. Below the roller bracket 52, a ring-shaped grinding wheel 56 is fixed by a bolt 54. A plurality of grinding grinding stones 58 arranged in a ring shape at intervals in the circumferential direction are fixed to the outer peripheral portion below the grinding wheel 56.

When the description is continued with reference to FIG. 7, in the singulation process, first, the back surface 2 a of the wafer 2 is directed upward, and the wafer 2 is attracted and held on the upper surface of the disk mounting table 46. Next, when viewed from above, the disk mounting table 46 is rotated counterclockwise at a specific rotation speed (for example, 300 rpm). In addition, when viewed from above, the disk mounting table 50 is rotated counterclockwise at a specific rotation speed (for example, 6000 rpm). Next, the rotating shaft 50 is lowered by the raising and lowering means (not shown) of the grinding device 44, and the grinding grindstone 58 is brought into contact with the back surface 2 b of the wafer 2. After that, the rotating shaft 50 is lowered at a specific grinding feed rate (for example, 1.0 μm / s). According to this, the back surface 2b of the wafer 2 can be ground, and the wafer 2 can be modified to a specific thickness (for example, about 100 μm).

Furthermore, during the grinding of the wafer 2, a specific pushing force due to the grinding feed acts on the wafer 2, so that the crack 60 goes from the modified layer 42 formed inside the semiconductor substrate 4 toward the thickness direction of the wafer 2. Grow. In the embodiment shown in the figure, as shown in FIG. 8 (b), in the cutting groove forming process, the cutting groove 30 that reaches the first memory layer 6 is formed because it passes beyond the bonding layer 8, so it is modified from The crack 60 that the layer 42 grows to reach the first memory layer 6 is not zigzagged and leads to a cutting groove 30. Therefore, as shown in FIG. 8 (a), using the lattice-shaped cracks 60 grown from the lattice-shaped modified layer 42 as a starting point of division, the wafer 2 can be appropriately divided into individual pieces along the predetermined division line 14. Flash memory chip 12. In addition, since the crack 60 growing from the modified layer 42 is used as a starting point for division, the interval between adjacent flash memory wafers 12 is substantially zero in quality. In addition, if the depth of the cutting groove 30 is at least the same as the thickness of the second memory layer 10, the crack 60 grown from the modified layer 42 will not bend in the bonding layer 8. In the illustrated embodiment, the modified layer 42 is removed by grinding, but the modified layer 42 may include the modified layer 42 even if the modified layer 42 is not removed.

After the segmentation project is implemented, the DAF segmentation project is implemented. The DAF is configured on the back surface 2b of the wafer 2 that is divided into individual flash memory chips 12. The DAF support tape is expanded to divide the DAF into each flash. RAM chip 12. In the DAF division process, first, a DAF62 having a circular shape having the same diameter as that of the wafer 2 is prepared. In the illustrated embodiment, as shown in FIG. 9, the DAF 62 is supported on a central portion of a circular support tape 66 fixed to a frame 64 having a ring-shaped periphery. Further, a DAF 62 is attached to the back surface 2 b of the wafer 2 divided into the flash memory chips 12 and disposed thereon. At this time, although the wafer 2 is divided into individual flash memory wafers 12, the shape of the disc-shaped wafer 2 is maintained by the protective tape 40. Next, as shown in FIG. 10, the protective tape 40 is removed from the surface 2 a of the wafer 2 divided into the individual flash memory wafers 12. Note that, in FIG. 10, a dividing line formed from the cutting groove 30 or the crack 60 is indicated by a reference numeral 68.

Then, the support tape 66 supporting the DAF62 is expanded to divide the DAF62 into each flash memory chip 12. The division of the DAF 62 can be performed using, for example, a part of the expansion device 70 shown in FIG. 11. The expansion device 70 includes a cylindrical expansion drum 72, a ring-shaped holding member 74 that is freely arranged radially outward of the expansion drum 72, and a holding member 74 that is attached to the holding member 74 at intervals in the circumferential direction. The upper outer periphery has a plurality of tools 76. The diameter of the expansion drum 72 is larger than the diameter of the wafer 2 and smaller than the inner diameter of the frame 64. In addition, the inner diameter and outer diameter of the holding member 74 are formed corresponding to the inner diameter and outer diameter of the frame 64 so that the frame 64 can be placed on the upper surface of the holding member 74.

When continuing the description with reference to FIG. 11, first, the wafer 2 divided into the flash memory wafers 12 faces upward, and the frame 64 is placed on the holding member 74. At this time, the upper surface of the holding member 74 is positioned at almost the same height as the upper end of the expansion drum 72 shown by a solid line in FIG. 11. Next, the frame 64 is fixed with a plurality of fixtures 76. Next, the holding member 74 is lowered by a lifting means (not shown) such as a cylinder. In this way, since the frame 64 is lowered together with the holding member 74, the support tape 66 fixed to the frame 64 is expanded by the expansion drum 72 which is relatively raised, and a radial tension acts on the support tape 66. Accordingly, as indicated by a two-dot chain line in FIG. 11, the distance between adjacent flash memory chips 12 is widened, and the DAF62 arranged on the back surface 2 b of the divided wafer 2 follows each flash. The memory chip 12 is appropriately (neatly) divided along the periphery of each of the flash memory chips 12. Further, each of the flash memory chips 12 on which the DAF62 is mounted on the back is mounted on a printed circuit board (not shown) or the like via an adhesive sheet, that is, the DAF62.

As described above, in the embodiment shown in the figure, during the division process, the crack 60 grown from the modified layer 42 is not guided to the cutting groove 30 in a meandering manner, so the wafer 2 can be guided along the planned division line 14 It is appropriately divided into individual flash memory chips 12. Furthermore, in the embodiment shown in the figure, since the crack 60 growing from the modified layer 42 is used as a starting point for division, the interval between adjacent flash memory chips 12 can be set to substantially zero, and In the embodiment shown in the figure, in the DAF division process, the DAF 62 can be appropriately (neatly) divided along the periphery of each flash memory chip 12.

In addition, before the cutting groove formation process is performed, DAF62 is arranged on the back surface 2b of the wafer 2 and it is considered that not only the second memory layer 10, DAF62, but also the first memory layer 6 and the semiconductor substrate 4 are used in the cutting groove formation process. Point of cutting together, and in the state where the back surface 2b of wafer 2 is equipped with DAF62, at the time of cutting, wafer 2 is shaken by the elasticity of the adhesive layer of DAF62, so it is on the back surface 2b side of wafer 2, A crack is generated inside the wafer 2, which may have a bad influence on the quality of the flash memory chip 12. However, in the illustrated embodiment, the DAF 62 is not provided on the back surface 2 b of the wafer 2 in the cutting groove formation process, and the cutting groove 30 is formed on the second memory layer 10. No crack is generated inside the wafer 2.

2‧‧‧ wafer

4‧‧‧ semiconductor substrate

6‧‧‧ the first memory layer

8‧‧‧Combination layer

10‧‧‧Second memory layer

12‧‧‧Flash Memory Chip

30‧‧‧ cutting groove

42‧‧‧ Reformed floor

60‧‧‧ Crack

62‧‧‧DAF

FIG. 1 (a) is a perspective view showing a state where a wafer is placed on a reel mounting table of a dicing apparatus, and (b) is a sectional view of the wafer.

FIG. 2 is a perspective view showing a state where a cutting groove forming process is performed.

FIG. 3 is a cross-sectional view of a wafer forming a cutting groove.

FIG. 4 is a perspective view of a state in which a protective tape is disposed on a surface of a wafer, and a wafer is placed on a disk mounting table of a laser processing apparatus.

FIG. 5 is a perspective view showing a state where a modified layer forming process is performed.

FIG. 6 is a cross-sectional view of a wafer forming a cutting groove and a reforming layer.

FIG. 7 is a perspective view showing a state where a division process is performed.

FIG. 8 (a) is a perspective view of a wafer divided into individual flash memory chips, and (b) is a cross-sectional view of a wafer divided into individual flash memory chips.

FIG. 9 is a perspective view of a state where a DAF is disposed on a back surface of a wafer divided into individual flash memory chips.

FIG. 10 is a perspective view showing a state where a protective tape is removed from a surface of a wafer divided into individual flash memory chips.

FIG. 11 is a perspective view showing a state in which the DAF is divided into each flash memory chip.

Claims (2)

A wafer processing method comprising alternately stacking a first memory layer connected to a surface of a semiconductor substrate with a plurality of metal films and insulating films, and alternately stacking the insulating layer as a bonding layer on the first memory layer. A plurality of flash memory chips composed of a plurality of metal films and a second memory layer of an insulating film are divided into predetermined flash memory wafers by dividing a predetermined line, and the wafer processing method is characterized in that: Consisting of at least the following projects: A cutting groove forming process is to form a cutting groove in the second memory layer by cutting a predetermined dividing line with a cutter; The reforming layer forming process is to position the light-condensing point of laser light with a wavelength penetrating to the semiconductor substrate within the semiconductor substrate corresponding to the predetermined division line, and irradiate the semiconductor substrate with laser light to form a reform Stratum corneum; and Dividing process involves grinding the back surface of a semiconductor substrate to grow cracks from the reforming layer and dividing the wafer into individual flash memory wafers; and In the DAF division process, a DAF is arranged on the back of a wafer that is divided into individual flash memory chips, and a DAF-supporting tape is expanded to divide the DAF into each flash memory chip. The method of processing a wafer as described in claim 1, wherein In the cutting groove forming process, the cutting groove reaches the bonding layer.